1. Field of the Invention
The present invention relates to a semiconductor device formed by droplet discharging as typified by an ink jetting method, and a method for manufacturing the semiconductor device.
2. Related Art
Conventionally, a so-called active matrix driving display panel or a semiconductor integrated circuit, each of which is composed of a semiconductor element as typified by a thin film transistor (hereinafter, TFT) over a glass substrate, is manufactured by patterning a various kinds of thin films by a light exposure process using a photomask (hereinafter, photolithography process).
By the photolithography process, resist is coated allover the surface of a substrate to be pre-baked, and an ultraviolet ray or the like is emitted thereto via a photomask, then, a resist pattern is formed by developing. Thereafter, a thin film (that is formed by a semiconductor material, an insulating material, or a conducting material) presented in a portion to be a film pattern is etched off by using the resist pattern as a mask pattern, and the thin film is patterned to form a film pattern, then, a semiconductor element is formed.
On the other hand, a bottom gate TFT is used as a driver element of a pixel of a liquid crystal display. In the bottom gate TFT, a gate electrode has a tapered portion at its edge portion to prevent electric field concentration at the vicinity of the edge portion of the gate electrode in a gate insulating film that overlaps with the gate electrode. Further, a tapered portion is provided to the gate electrode to improve step coverage of the gate insulating film provided over the gate electrode (Unexamined Patent Publication No. 10-170960).
However, in order to form a gate electrode having a tapered portion, processes of etching, cleaning, and drying are required to be repeated at plurality of times in addition to the photolithography process. Therefore, there have been problems that most materials for the gate electrode and the resist are wasted, and throughput becomes deteriorated since a large number of processes for forming the resist mask pattern and the gate electrode is required in a manufacturing process of a semiconductor device.
It is difficult for an exposure device used for the photolithography process to perform exposure processing of a large substrate at once. Therefore, a manufacturing method of a semiconductor device using a large substrate has problems that exposure processing is required to be performed at a plurality of times and manufacturing yields are deteriorated due to a mismatch between adjacent patterns.